A set of experiments is proposed to validate and further develop a new nanoparticle based technology, Nanoparticle induced Circuit excitation (NICE), for modulating the activity of cells remotely and non-invasively. A fundamental goal of biology is to understand the role of each cell type in a complex organism. The definitive test of cell function is to selectively turn on or off the activity of a single cell type in a living animal and examine the effect on physiological function. Recent tools, such as light activated ion channels such as channel rhodopsin, have pioneered the external control of membrane potential in genetically defined cells and established a new means for investigation by neuroscientists. However, these optical methods have practical disadvantages limiting their application including the need for surgical implantation of invasive fiber optics; the inability to stimulate cells in multiple anatomical regions simultaneously; and the difficulty of modulating multiple cell types in parallel. We address this challenge by using nanoparticles to activate defined cell populations remotely with radiowaves. Ferrous oxide coated with streptavidin is used to decorate cells, which express a biotin acceptor protein under the control of cell specific promoters. These same cells are engineered to also express TRPV1, a single component, temperature-sensitive ion channel that can detect small changes in temperature within the physiological range and by conformational change allow graded calcium entry. Exposing the metal coated cells to a defined electromagnetic field increases the local temperature and activates TRPV1 channels resulting in a Ca2+ current and cell activation. We have preliminary data that confirms the efficacy of this method in vitro and now propose to extend our studies to further validate the technology in vitro and to modulate in vivo functions such as hormone release and neural activity. We will also establish a means for combinatorial activation of different cells using a modified TRPV1 and nanoparticles fabricated from other metals that can be excited at different wavelengths. We will use this tool to examine the roles of specific peripheral and CNS cell populations in energy metabolism. We propose to develop this method in three stages: 1) Validate the safety and utility of NICE in vitro and refine the methodology by decorating different cell types with distinct particles tuned to different wavelengths to activate ensembles of different cell populations in various combinations. 2) Establish the ability of NICE to modify hormone release to regulate glucose metabolism in diabetic animals in vivo. 3) Show that NICE can be used to stimulate action potentials in electrically excitable cells to modify behavior and use NICE to investigate the role of specific hypothalamic populations in (NPY and POMC) to control appetite. In time, NICE may be adapted for clinical uses, e.g: induced pluripotent stem cells engineered to express NICE constructs may act as autografts to enable external control of cell function. These applications are distant but not inconceivable and the studies proposed may form the foundation for the clinical use of nanoparticles.